I am looking for suggestions on good retrogames that are playable by 2 players at the same time, but where players are on the same side instead of against each other. All genres allowed, although I would prefer to avoid fighting or battle games, since the players will be my children. My purpose is to let them play together instead of always taking turns

By the way, when I say "retro" I mean at least 20 years old

Some easy choices would be Bubble Bobble, Mario Bros, and Silk Worm.

Bruce Lee on the C=64 can be played cooperatively, and despite the kung fu theme it's not really violent.

Bloodwych - I've fond memories of this split screen 2 player RPG, which I played on C64. Decent spell list, 4 characters per party, plenty of floor puzzles, even trade & bartering with NPCs.

Excellent game for its time, never really found anything like it since.

Another decent 2 player co-op game is Wiz n Liz from Psygnostic, which I recall playing on the Megadrive. A charming game with wizards and rabbits, so depending on the ages of your children it might be visually quite appealing too. A few years ago they released an official free to play flash browser version too , but don't think its accessible anymore.

Easily Rampage. Pretty awful in one player, it becomes awesome when a second player joins. Never played in 3 player so not sure how that goes. But the game is designed for multi-play, with some really fun stuff to do (tennis-tramcar anyone?). Plus you can punch your mate if they're doing your head in (plus EAT them if they turn back human!)

I could swear there was a website with fully searchable information on every arcade coin-op game ever made including variants and bootlegs... and I was hoping it would also allow searches by number of players supported. I think it allowed other kinds of narrow searches such as by controls (e.g. spinner, trackball, double joystick...). But I could not find that website at all, damn me for not bookmarking it back then Anyone knows what website it could have been, and if it still exists?

I could swear there was a website with fully searchable information on every arcade coin-op game ever made including variants and bootlegs... and I was hoping it would also allow searches by number of players supported. I think it allowed other kinds of narrow searches such as by controls (e.g. spinner, trackball, double joystick...). But I could not find that website at all, damn me for not bookmarking it back then Anyone knows what website it could have been, and if it still exists?